1. Field of the Invention
The present invention relates generally to sealing subterranean zones penetrated by well bores, and more particularly, to foamed epoxy resin compositions which set into corrosion resistant highly resilient solid masses and methods of using the compositions in the construction and repair of wells.
2. Description of the Prior Art
Hydraulic cement compositions are commonly utilized as sealants in subterranean well construction and repair procedures. For example, hydraulic cement compositions are used in primary sealing operations whereby strings of pipe such as casing and liners are sealed in well bores. In performing primary cementing, a hydraulic cement composition is pumped into the annular space between the walls of the well bore and the exterior surfaces of pipe disposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The cement sheath physically supports and positions the pipe in the well bore and bonds the exterior surfaces of the pipe to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented.
The development of wells including one or more laterals to increase production has recently taken place. Such multi-lateral wells include vertical or deviated principle well bores having one or more ancillary laterally extending well bores connected thereto. Each of the lateral well bores can include a liner sealed therein which is tied into the principle well bore. The lateral well bores can be vertical or deviated and can be drilled into predetermined producing formations or zones at any time in the productive life cycle of the well.
When conventional cement compositions are utilized for sealing casing or liners in well bores, they set into brittle solid masses which often do not have sufficient resiliency, i.e., elasticity and ductility, to resist loss of pipe or formation bond, cracking and/or shattering as a result of pipe movements caused by expansion, contraction, impacts or shocks. The bond loss, cracking or shattering of the set cement allows leakage of formation fluids through at least portions of the well bore or bores by way of the annuluses therein which can be highly detrimental.
Hardenable epoxy resin compositions have heretofore been used for sealing subterranean zones penetrated by well bores when the zones contain corrosive fluids. For example, waste fluids such as salt water, acidic materials, caustic materials, organic materials, chemical by-product materials, and the like are often disposed of by injecting them into disposal wells. Such disposal wells penetrate subterranean formations which accept large volumes of waste and are naturally separated from other subterranean formations. When a disposal well or other well containing corrosive fluids is completed in the conventional manner whereby a string of steel pipe is cemented in the well bore utilizing a hydraulic cement slurry, both the cement and steel casing are often subjected to severe corrosion. A result of such corrosion in disposal wells can be that the liquid waste materials leak into and contaminate formations containing useful fluids such as hydrocarbons or potable water. In other wells where hydrocarbons are produced along with corrosive fluids, the corrosion can result in leakage of fluids between formations and/or to the surface.
In order to prevent the corrosion of metal pipe strings and insulate them from corrosive fluids, it has heretofore been the practice to seal the pipe strings in well bores with a hardenable epoxy resin composition. Epoxy resin compositions are highly resistent to degradation by acids and other corrosive fluids and their use ensures that the corrosive fluids do not find their way to the surface or into subterranean locations containing useful recoverable fluids. However, like set cement compositions, hardened epoxy resin compositions often have not had sufficient elasticity to resist failure as a result of pipe movements.
Thus, there are needs for improved hardenable sealing compositions for use in the construction and repair of wells whereby the sealing compositions are corrosion resistant and also have sufficient resiliency to resist failure caused by pipe movements.